A. Field of the Invention
This invention relates to the field of golf club heads and methods for their manufacture. More particularly, the invention relates to fiber reinforced plastic golf club heads, golf club heads that are made by injection molding, golf club heads that include structural features to optimize the distance a golf ball may be propelled, golf club heads that have a large preferred striking surface or "sweet spot", golf heads that absorb vibrational forces rather than transferring them to the hands and arms of the user, golf club heads that have structural features to stabilize the club when striking a ball, and golf club heads that include weight adjustability features.
B. The Background Art
Prior to the invention, golf club heads were typically divided into groups called "woods" and "irons" based on the type of material from which they were made. Woods were typically used when it was desired to propel a golf ball a long distance and irons were used to propel a golf ball a shorter distance. Many different golf club head designs have been tried in the prior art, with most emphasis being placed on propelling the golf ball the greatest possible distance. Typically, woods were made of a cellulose material and had a metal sole plate for weight, balance and durability.
1. Golf Club Heads with Cavities
In the prior art, there are several golf club heads that have cavities for different purposes, and related features. In U.S. Pat. No. 3,556,532, issued in the name of James E. Ballmer, a golf head is disclosed that was formed from a body and included a number of cavities in the body. The cavities provided the golf club head with acoustical qualities upon striking a golf ball. This design allowed a golf club head to be made from a non-cellulose material, such as plastic, with sound qualities that emulate the sharp, high frequency sound of a traditional wood striking a golf ball. However, the '532 patent illustrates and claims only cavities which are formed in the bottom of the club head.
In U.S. Pat. No. 5,445,382, issued in the names of Terry V. Pearce and Tony M. Pearce, a golf club head is disclosed which is made from injection molded long fiber reinforced plastic where the fibers are entangled with each other for increased stiffness. That patent also discloses a structure that includes cavities in the bottom of the golf club head, the cavities being covered by a sole plate in the assembled club head.
U.S. Pat. No. 5,346,217, issued in the names of Kazuhiro Tsuchiya, Toshiharu Hoshi, Atsushi Tsuchida, and Kenzaburo Iijima, discloses a metal alloy golf club head with a hollow interior. U.S. Pat. No. 5,060,951, issued in the name of Dillis V. Allen, discloses an enlarged face golf club head made from a thick-walled metallic material and having cavities in a honeycomb pattern behind the striking face. U.S. Pat. No. 5,067,715, issued in the names of Glenn H. Schmidt, John P. Sheehan, and Richard C. Helmstetter, discloses a metal golf club head that has shock wave distributing dendrites within its interior. U.S. Pat. No. 3,468,544, issued in the name of Anthony J. Antonious, discloses an aerodynamic golf club head having passages through which air may flow when the head is swung at a golf ball. The passages open at one end through the top of the striking face and at the other through the opposite side at a lower position. U.S. Pat. No. 2,460,435, issued in the name of Fred B. Schaffer, discloses a golf club head that includes a plurality of voids that are preferably arranged radial to the core with separating ribs, the arrangement of voids and ribs being such that strength and stress transmission are achieved. U.S. Pat. No. 1,592,463, issued in the name of Theodore Marker, discloses a metallic golf club head with internal webs to connect the striking face of the head with the rear wall of the head. U.S. Pat. No. 4,630,826, issued in the names of Susumu Nishigaki, Akio Ohkoshi and Torao Aozuka, discloses a golf club head that includes ceramic plates and laminated layers of fiber with an internal cavity.
None of the above-identified patents disclose the presence of a golf club having cavities which are open to the top of the club. Nor do any of those patents disclose a golf club head having an integrally formed sole plate. Thus, manufacture of the prior art golf club heads with cavities requires assembly of at least a club head and a sole plate. Further labor may also be required in finishing the assembled portions of the club head to provide it with an aesthetically pleasing appearance.
2. Golf Club Heads Including Inserts and Attachments
Also in the background art, there were various golf club heads that included inserts and attachments of various types. For example, U.S. Pat. No. 2,067,556, issued in the name of William L. Wetlaufer, discloses an adjustable golf club with complex sole plate attachment features. In U.S. Pat. No. 3,457,445, issued in the name of Benjamin T. Hardesty, a golf club head is disclosed that is made from plastic and has a separate faceplate. A plug is provided to secure the faceplate in position. In U.S. Pat. No. 4,687,205, issued in the names of Ichiro Tominaga and Teruo Sasaki, a golf club head is disclosed that includes a composite head of resin and fibers and heavy metal inserts. The '205 patent describes embedding of the heavy metal inserts within the club head to provide additional weight thereto. U.S. Pat. No. 5,467,989, issued in the names of Robert Good and Richard Carobus, discloses a golf club head made from a solid, unitary mass of acrylic with a metal insert. The metal insert of the '989 patent holds the club shaft in place on the club head.
The use of a separate face plate, as disclosed in the above patents, increases the manufacturing, materials, and finishing costs of those golf club heads. Further, none of these patents disclose a feature which allows for varying the weight of the club or weighting located along the arc of a normal golf swing.
3. Golf Club Heads Made From Various Non-Typical Materials
In U.S. Pat. No. 4,204,684, which issued in the name of Robert P. Molitor, a golf club head and related production method are described where laminated resinous or plastic materials were bonded together to form a composite head. Some layers of the head had different characteristics than others to provide a dimensionally stable and durable golf club head with high impact resistance and approximately the same density of a wooden golf club head.
U.S. Pat. No. 5,007,643, issued in the names of Takahuru Okumoto, Tatsuo Nishimoto and Hideaki Wakaki, discloses a golf club head that uses an outer shell made of a fiber-reinforced resin and a core made of a syntactic foam, the core having both resin with glass microballoons and whiskers therein. U.S. Pat. No. 5,009,425, which issued in the names of Takahuru Okumoto, Toshio Ninomya and Tstsuya Hayashi, describes a golf club head with an outer shell made from fiber-reinforced resin and a core within the outer shell, the core being made from a high specific gravity metal powder within a thermoplastic resin. The core may include reinforcing fibers.
In U.S. Pat. No. 1,854,548, issued in the name of James B. Hunt, a golf club head is disclosed made from spring metal. In U.S. Pat. No. 4,883,623, issued in the names of Itsushi Nagamoto, Tatsuo Nakanishi and Tomoharu Yamashita, a method for making a golf club head from fibrous material is disclosed. In U.S. Pat. No. 5,056,705, issued in the names of Saburo Wakita, Junji Hoshi, Shinich Miyamoto and Hideo Kawabata, a method for making a golf club head from a precision cast metal such as titanium or an alloy is disclosed. In U.S. Pat. No. 1,864,513, issued in the name of Jack H. Balch, a golf club head made from layers or plies of an appropriate fabric such as duck canvas is disclosed. U.S. Pat. No. 4,664,383, issued in the name of Yuichi Aizawa, discloses a golf club head that includes resin with woven and non-oriented fibers. U.S. Pat. No. 5,154,425, issued in the names of Paul W. Niskanen, Danny R. White, March G. Mortensen and Stanislav Antolin, discloses a golf club head which is made from metal matrix composite and/or ceramic matrix composite materials. U.S. Pat. No. 5,100,144, issued in the names of Takahuru Okumoto and Tetsuo Hayashi, discloses a golf club head made from a fiber-reinforced resin. U.S. Pat. No. 4,793,616, issued in the name of David Fernandez, discloses a golf club head which includes a composite material molded to a hard, high density material. U.S. Pat. No. 4,754,975, issued in the name of Yuichi Aizawa, discloses a golf club head which includes an inner layer of non-metallic fiber reinforced synthetic resin. U.S. Pat. No. 4,650,626, issued in the name of Ikuji Kurokawa, discloses a method for making a golf club head, the method including the step of heat pressing a compound in a mold.
Many of the materials described and manufacturing processes used and/or disclosed in the above patents disclosed above are costly. None include cavities which open to the top of the club or a mechanism which imparts the club with weight variability along the arc of a normal golf swing.
Each of the documents disclosed above is hereby incorporated by reference in its entirety for the material disclosed therein.
What is needed is a durable golf club head that is economical to produce. A low-cost, light weight golf club head is needed which optimizes the distance a golf ball may be propelled. Further, a golf club head is needed with the above advantages and which has a large preferred striking surface or "sweet spot". A golf club head which absorbs vibrational forces is also needed. Further needs include weight/momentum adjustability and improved structural stability.